Felow

Trying to restore a 1989 K100RS that has been standing still for 10 years and have run into some problems on the way.

Thins I've done so far is:

Change all the fuel lines

New fuel pump and fuel filter

Oil change

New fuel injectors(The old ones didn't work anymore)

Cleaned the throttle body

New spark plugs DPR8EA-9 ( not sure these are correct?)

Now the problem is when I start it after it has been standing still for a couple of days it backfires and then gas comes dripping out of the exhaust.This is where I am stuck at the moment and would like some feedback.

Also, I am unsure of the spark plug wires are correct since I accidentally took them off without marking the order of them. But I have got the bike running with only using starting gas.

92KK 84WW Olaf

Life time member

Number of posts : 6582

If yours is a 16v engine then plug with R in it is correct as it uses resistor plugs. If its a 2v then use plugs without R, they don't use resistor plugs.

I am guessing here but wonder are you getting gas pressure too high due to a faulty fuel pressure regulator. This is in between the throttle bodies and airbox on 2v engines, with a vacuum line from the end of the throttle bodies beside the coils that is routed into it. If that's cracked no vacuum, bad running and fuel pressure way too high. You also have 3 vacuum caps.....again same effect.

But standing a few days and gas coming out is also possibly suggesting an alternative of fuel leaking in.....injectors are normally the only way that happens, as in stuck open. Pull plugs before firing up and check each cylinder....should all be clear at that point.

MartinW

Life time member

Number of posts : 1094

A faulty temperature sensor or bad connection can cause over fueling. There is a procedure for testing on this site. Try starting the bike with # 6 Kraffstoppe fuse removed, you will have to manipulate the throttle. It should start but run badly and as the engine starts to die ram the fuse back in. It helps if you have two people one on the throttle and one on the fuse.

norton71

Silver member

Number of posts : 118

Backfiring and fuel in the exhaust? ...I trust you are not twisting the throttle whilst trying to start a fuel injected bike....don't touch the throttle at all!, just hit the start button (with the fast idle/choke set on the first notch)

92KK 84WW Olaf

Life time member

Number of posts : 6582

Getting at the temp sensor will also tick off a few other jobs like cleaning and flushing the rad/cooling system, checking the fan, cleaning filler cap, cleaning out a few other electrical connections under the tank.......

Felow

Two Wheels Better

Moderator

Number of posts : 3917

A local aftermarket BMW tech had a K75 in his shop recently that would piss fuel when cranking. He looked at 'everything' and was quite frustrated. Turned out to be a loose connector plug up to the AFM unit and a slightly sticking flap. Runs a charm after a bit of fiddling.